The geniuses running the Republican campaign effort in Florida have now decided that stirring opposition to medical marijuana will help Gov. Rick Scott win.

Casino billionaire Sheldon Adelson, a huge donor to pro-Scott forces, recently gave $2.5 million to a new group aiming to defeat a proposed constitutional amendment that would legalize cannabis use for patients with cancer, glaucoma, multiple sclerosis and six other serious diseases.

Recent polls show that between 66 percent and 70 percent of likely Florida voters favor the medical-marijuana amendment, and that the support cuts broadly across party lines. The measure, listed as Amendment 2 on the November ballot, requires 60-percent approval to become law.

The question is why the Republican brain trust thinks it’s a crackerjack idea to attack a popular social cause while Scott is fighting tooth-and-nail to save his job. The governor will be in deep trouble if thousands and thousands of marijuana advocates show up to vote in November. They’re not exactly his core constituency, so why get them riled?

Scott’s opposition to the medical-marijuana amendment is well known. He should low-key the issue, except to point out that he has promised to sign a law allowing a non-euphoric strain of the herb to be used for treating severe epilepsy in children and other patients.

You might wonder why a rich Las Vegas casino owner is trying to prevent sick people 2,000 miles away from gaining legal access to pot. You think Adelson is genuinely worried that medicinal cannabis is a gateway to total legalization, and that it poses a dire threat to the people of Florida?

According to The Washington Post, during the 2012 election cycle Adelson spent more than $92 million on political races, most of it on losing candidates. He wasted a ton of dough on Newt Gingrich’s flaccid presidential run, and then dumped more on Mitt Romney.

Now someone apparently has convinced him that Scott’s re-election depends on a large turnout of anti-pot voters. Thirty years ago this might have been a viable strategy, but public opinion has shifted drastically all over the country.

The GOP isn’t really scared of medicinal marijuana. They’re scared that it’s on the same ballot with Scott and their other candidates. They’re scared that more pro-cannabis voters will be Democrats than Republicans.

Feeding that fear is the fact that the biggest booster of Amendment 2 is John Morgan, a wealthy Orlando trial lawyer who’s a top supporter (and employer) of Charlie Crist, Scott’s presumed Democratic opponent in November.

A longtime proponent of legalizing medical marijuana, Morgan spent about $4 million on the statewide petition that put the issue on the ballot. Clearly he believes it won’t hurt Crist’s chances in the governor’s race.

So the Republicans now retaliate with the Drug Free Florida Committee, headed by GOP fundraiser Mel Sembler and his wife, who have close ties to the Bush family. The Semblers also bankrolled the fight against legalizing marijuana in Colorado.

Adelson’s $2.5 million check is by far the heftiest donation to the fledgling committee. When asked why the out-of-state gambling tycoon is pouring so much money into the battle against Amendment 2, Scott replied: “You’d have to ask Sheldon.”

As if Scott has no clue what his sugar daddy is up to. It’s an organized plan by Republican strategists that has nothing to do with the medical dispensation of marijuana, the statutory sturdiness of the amendment, or the ludicrous fantasy of a “drug-free” Florida.

It’s raw politics. The platform will be a 21st-century version of Reefer Madness propaganda, and the aim will be to scare people enough to make them go vote against Amendment 2. Those are folks who would also likely vote for Scott.

That’s the GOP theory, anyway.

A hyperbolic media campaign against medical marijuana could easily backfire, motivating pro-pot voters in even larger numbers. A high turnout, no pun intended, can only help Crist and hurt Scott.

If a smart person were making his campaign decisions, the governor would have told Adelson to stay out of Florida’s marijuana debate. Amendment 2 is almost certain to pass, so why run commercials that will only propel more of its supporters to the polls?

The result could extend Adelson’s losing streak, and send Scott’s re-election hopes up in smoke.